Drop out fuse construction having a fuse tube which is resiliently mounted in an annular support member



Aprll 6, 1965 R. M CLOUD 3,177,317

DROP OUT FUSE CONSTRUCTION HAVING A FUSE TUBE WHICH IS RESILIENTLYMOUNTED IN AN ANNULAR SUPPORT MEMBER Filed July 22,1960 2 Sheets-Sheet IIN V EN TOR. kaea: A. flfckaua Y April 6, 1965 MCCLQUD 3,177,317

DROP OUT FUSE CONSTRUCTION HAVING A FUSE TUBE WHICH IS RESILIENTLYMOUNTED IN AN ANNULAR SUPPORT MEMBER Filed July 22, 1960 2 Sheets-Sheet2 IN V EN TOR.

yamwfw United States Patent 3,177,317 Dlifil @UT FUSE CflNfiTRUQTlUNHAVHNG A FUSE TUBE WHMIH l) RESELEENTLY MGUNTED IN AN ANNULAR SUEPGRTMEMBER George R. McCloud, hearth lt lilwauhee, Win, assignor toMeGraw-Edison Company, Milwaukee, Wis, a corporation of Delaware Filedfully 2.2, 196d, Ser. No. dhtitiil 8 Qlaims. (Cl. Nth-114) Thisinvention relates generally to fuse cutouts and more particularly to animproved fuse cutout wherein recoil forces developed incident to currentinterruption are dissipated in the fuse tube itself.

Generally fuse cutouts are so constructed that upon over-currents thefuse link within the fuse tube ruptures causing an arc to be drawnbetween the severed ends of the link. The arc so created induces asignificant temperature rise within the fuse tube which causes the fusetube or fuse liner to evolve deionizing gases from the inner surfacethereof. The gases so evolved tend to extinguish the arc and to therebyinterrupt the flow of current through the fuse tube.

The gases, in evolving at an extremely rapid rate within the limitedconfines of the fuse tube bore, develop a relatively high pressure.Hence provisions are made to vent the fuse tube thusly allowing thegenerated gases to escape therefrom. Commonly one end of the fuse tubeis left open and an expendable cap (similar to that described in PatentNo. 2,702,842 issued February 22, 1955 to lepsen et al., and assigned tothe same assignee as the present invention) is utilized to close theother end of the tube. This construction provides single ventedoperations on low fault currents and double vented operation onrelatively higher fault current conditions. During high currentinterruption in a fuse cutout utilizing an expendable cap on the upperend of the fuse tube, the gases initially escaping from the lower end ofthe tube impart an upward thrust to the tube. After the expendable caphas blown the thrust is generallyreversed i.e., a downward force isexerted on the fuse tube.

In the case of single vented fuse tubes (those not utilizing anexpendable cap) the thrust is generally unidirectional. (O-pposite tothe direction of the escaping gases.)

In either event, sometime during the current interrupting cycle, arelatively large thrust force is exerted on the fuse tube and the cutoutassembly in general.

Prior art fuse cutouts have attempted to realize structures which willabsorb or otherwise dissipate this thrust force. 7

One means of dissipating thrust forces, quite frequently used by theprior art devices, is to make the component parts of the cutout largerand more capable of absorbing impact forces. However, this is expensiveand results in bulky oversized cutouts.

Another method of dissipating thrust forces is to mount the fuse tube onthe porcelain insulator by means of a resilient support member. Whiledeformation of the support member serves to absorb some of the recoilforces, in practice, a portion of these forces must normally be absorbedby the porcelain insulator, a condition which may lead to rupture of theporcelain.

I have found that by resiliently mounting the fuse tube with respect toits supporting members and the rest of the cutout that a maximum amountof thrust dissipation may be achieved at a minimal cost.

It is therefore an object of this invention to provide a fuse cutoutwherein thrust forces are substantially dis sipated in moving the fusetube relative to the rest of the cutout.

Another object of the invention is to provide a fuse cutout that isinexpensive to build and which has very little tendency to malfunction.

A further object of the invention is to provide a fuse cutout thatfunctions to effectively dissipate thrust forces occurring in bothdirections along the fuse tube.

A still further object of the invention is to provide a fuse cutoutwherein premature separation of contacts is substantially eliminated.

Other objects and advantages of my invention will be apparent from thefollowing description of the preferred embodiments of the inventiontaken in connection with the accompanying drawings in which:

FIG. 1 is a partially cutaway view in elevation of the invention;

FIG. 2 is a partially cut away view in elevation of a portion of thedevice of FIG. 1.

FIG. 3 is a partially cutaway view in elevation of one embodiment of theinvention.

Referring now to FIG. 1 there is shown a fuse cutout indicated generallyas 1 and comprising a porcelain insulator 2 having aflixed thereto anupper contact assembly 3 and lower trunnion supports 4 and a fuse tubeassembly 5 bridging the space between members 3 and 4.

The upper contact assembly 3 comprises a support member 6 which isailixed to insulator 2 by means of through bolt 7 and nut is. AnL-shaped member d is attached to support 6 by fastening means it andextends upwardly of the insulator 2. A terminal reception member may beattached to the upward extremity of member to receive a line wire butthis is not shown.

Aflixed to support a is a hood member 11 which has a curvate top portion12 with a slot 1.3 therein and a pair of laterally projecting sideportions 14. Attached to the underside of the inwardly projecting leg 15of L-shaped member 9 is a pair of curvate spring contacts 16 whichgenerally follow the configuration of the curvate top portion 12 of thehood 11. Enlarged contact faces 17 may be provided at the free end ofcontacts 16 in order to increase the contact area.

A spring biased latch 18 is pivotally affixed to support member 6 andextends between contacts 16 and through slot 13 in top 12 and is adaptedto move along the axis of the slot. The latch 18 is provided wtih a cutaway face portion 18' and a locking shoulder portion 19 behind the faceof the latch.

A member 20 is afiixed to the upper end of a fuse tube 21 and has aferrule portion 22 containing a bore 23 therein which communicates withthe interior of the fuse tube 21. The other end of the bore 23 may beenclosed by an expendable cap 24-. Extending transversely from member 2iis a contact arm 25 having an enlarged contact facial surface 26 on theend thereof. Immediately behind the facial surface 26 is a shoulderportion 27 which is adapted to normally engage the shoulder portion 19of latch 18 to provide positive locking therebetween. It can be seenthat when latch 18 and contact 25 are in engagement with one anotherthat contact facial surface 26 is in contact with the enlarged contactfaces 17 of spring contacts 16.

Pivotally attached to member 2% by means of a pivot pin 20 is anintegral pull ring and unlatching member 28 which comprises a pull ring29 on one side of pin 2b and an elongate unlatching arm 39 which isnormally in com tact with th elower surface of latch 18. Thusly when thefuse tube 21 is in circuit bridging position, downward movement on pullring 29 will cause arm 34) to force latch 13 upwardly allowing the fusetube assembly to become unlatched.

Surrounding the lower end of fuse tube 21 is a sleeve member 31. Thesleeve member 31 has a laterally projecting portion 32 (FIG. 2) which isshouldered at its outer end at 33. A portion of the member 31 is removedat 34 so that entrance may be made to a portion of the fuse tube 21within the sleeve. A collar member 35 is firmly aflixcd to the lowerarea of the fuse tube 21 as by fastening means 36.

The bore through the sleeve member 31 is increased in steps to themiddle of the member and thence decreased in the same manner. Theannular shoulders so created are delineated as 37, 38, 38' and 37.

Helical compression springs 39 and 4t) are attached to the top andbottom of collar 35 and surround a portion of the fuse tube 21. Theupper spring 39 is bottomed at its upper end against shoulder 37 ofmember 31 and the lower spring 40 is bottomed at its lower end againstshoulder 37' of member 31.

Thusly fuse tube 21 is floating within the sleeve 31 and is capable ofaxial movement with respect to the sleeve to the extent that collar 35can move before abutting against shoulders 38 and 38'.

A pair of diamond shaped lug members 41 project outwardly from bothsides of the upper area of sleeve 31. Adjacent the lugs 41 is a throughpivot pin 42 which serves as the pivot for hinge contact 43. Hinge 43has a lip portion 43 near the upper side thereof which is designed tocontact lugs 41 and therefore limit the extent of movement between thehinge and sleeve members.

At the lower end of hinge member 43 are a pair of projecting bearingmembers or trunnions 45 which engage with lower trunnion supports 4 tosupport the fuse tube assembly.

Spaced inwardly of the bearing members 45 are cammed contact surfaces 46which normally engage with resilient contacts 47 on the inner side ofthe lower trunnion supports 4. A pivot pin 48 extends between thebearing members 45 (FIG. 2) and a fuse link fiip out lever 49 is mountedthereon. A torsion spring 50 is also mounted on the pin 48 and normallybiases lever 49 in a clockwise direction relative to FIGURE 2.

A lip portion 51 is provided on lever 49 and is adapted to engage withshoulder 33 on sleeve 31 to prevent relative motion between the sleeve31 and hinge 43. That is, when a fuse link 52 is positioned within thetube 21 and anchored at its lower end to the hinge member therebydrawing up lever 49 against the action of spring 50, the engagement oflip 51 and shoulder 33 will prevent movement between the sleeve andhinge until the fuse link is ruptured thereby allowing the lever topivot out of locking engagement with the sleeve.

When the fuse link is ruptured the flip out lever 49 pivots out ofengagement with the sleeve, the hinge 43 pivots around pin 42 andtrunnions 45 and the fuse tube drops down until the diamond shaped lug41 and lip 43' interengage at which time the hinge and fuse tube pivotaround trunnions 45 as a unit in a clockwise direction.

It should be noted that the nature of the contact between the upperresilient contacts and the upper contact on the fuse tube is a wipingaction so that axial movement of the tube will not break contactengagement.

In operation when a fault current is experienced the fuse link ruptures,an arc is struck, gases are evolved from the fuse tube tending toextinguish the are and then gases are vented from the tube with anaccompanying thrust force on the tube.

This thrust force is largely absorbed by compression of the springs 39and 40 since energy is required to move the tube against the biasingaction of the springs.

Typically the predominant thrust will be directed in an upward directionthusly compressing spring 39. When the spring reaches maximumcompression or when collar 35 abuts against annular shoulder 38 the fusetube and collar will tend to be forced in the opposite direction whichwill cause compression of the spring 40. It the case of a cutoututilizing an expendable cap the sequence of spring action is firstcompression of spring 39 then after the cap blows compression of spring40. Each time one or the A other of the springs is compressed work isdone and forces dissipated in so doing. Note that each time one of thesprings is compressed the other of the springs is elongated (tensioned)thusly adding to the energy dissipated.

It is important that the springs 39 and 4t be so coordinated that thecollar member is normally positioned midway between the annularshoulders 33, 38. In this respect the lower spring 4% may be somewhathigher rated than the upper spring since the force of spring latch 18and the weight of fuse tube 21 normally tend to compress the lowerspring.

While two compression springs are shown it is possible, particularly onsingle vented cutouts, to eliminate one of the springs since movement ofthe tube under the impetus of the force exerted by the escaping gases isin general uni-directional.

I have found that by using the heretofore described structure that verylittle recoil is experienced in the component parts of the fuse cutoutother than in the fuse tube, the movement of which is designed todissipate thrust forces.

In addition cutouts constructed according to this principle sufferlittle or no hangar bracket detformation, porcelain rupture, or othercomparable structural failures.

The embodiment of FIGURE 3 is similar to that of FIGS. 1 and 2 exceptthat the springs 39 and 4d are replaced by a shock isolator 61 which maybe of rubber, plastic or any other shock absorbing material.

Member 31 of FIG. 3 has an enlarged bore 66 therein. Afiixed to the.sides of the bore 60 is a thick inner layer in of rubber, plastic or asimilar material which is somewhat resilient and shock absorbent andwhich has the capacity of acting as a shock isolator. The fuse tube 21extends through the shock isolator 61 and has affixed thereto atpositions above and below the layer 61 nuts or collar means 62 orsimilar members which overlie a portion of the layer 61. A portion 32 ofthe member 31 projects laterally from the fuse tube and culminates in ashoulder 33' which as before is adapted to engage a portion of the flipout lever 49. A hinge like that of FIGS. 1 and 2 (43) is pivotallyattached to the sleeve 31 in the same manner as before but this is notshown.

The modification of FIG. 3 operates in the same manner as that of FIGS.1 and 2 except that thrust energy is expended in compressing first oneend and then the other of the layer 61. This particular modification hasthe advantage that in not having springs the damage due to corrosionwill be reduced.

While the layer 61 is indicated as being afiixed to the member 31 and infrictional engagement with tube 21, it is within the scope of thisinvention to affix the layer to both the sleeve and fuse tube therebyeliminating the collar members but this is not shown.

Both embodiments serve to substantially dissipate the thrust on the fusetube without experiencing destruction or fatigue of component parts orpremature fuse tube or contact separation.

While two particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that variouschanges and modifications can be made therefrom without departing fromthe invention and, therefore, it is intended for the appended claims tocover all such changes and modifications as fall within the true spiritand scope of the invention.

I claim:

1. In combination with a dropout expulsion fuse cutout having anelongated insulating member, a lower stationary contact and a springbiased upper stationary contact mounted in spaced apart relation on saidinsulating member, a gas evolving expulsion fuse tube, an upper movablecontact on said fuse tube normally engaging said spring biased contactand being continuously engageable therewith through limited axialdisplacement of said fuse tube, and a rupturable fuse link extendingaxially through said fuse tube and being electrically connected to saidupper movable contact and normally electrically bridging said lower andupper stationary contacts; a sleeve member supported on said lowerstationary contact and being in radially spaced apart surroundingrelation to the lower end of said fuse tube, an annular member of shockabsorbing material having its external surface affixed to the bore ofsaid sleeve member and its internal surface in con tiguous surroundingrelation to said fuse tube, means on said fuse tube for engaging saidmember of shock absorbing material so that said fuse tube is supportedin a normal position relative to said sleeve member against axialdisplacement in upward and downward directions, said fuse tube beingfree to move axially relative to said sleeve member and said member ofshock absorbing material returning said fuse tube to said normalposition after the thrust forces resulting from expulsion of gas fromsaid fuse tube incident to rupture of said fuse link subside, wherebysaid thrust forces are substantially dissipated by axial upward anddownward displacement of said fuse tube against said member of shockabsorbing material.

2. In a fuse cutout, an elongated insulating member, a lower stationarycontact and a spring biased upper stationary contact mounted in spacedapart relation on said insulating member, a gas evolving expulsion fusetube, an upper con-tact affixed to said fuse tube and normally engagingsaid spring biased contact, said upper and said spring biased contactsbeing in continuous engagement through limited axial displacement ofsaid fuse tube, a hinge contact member supported on said lowerstationary contact, a sleeve member surrounding the lower end of saidfuse tube and being pivotally mounted on said hinge contact member andhaving upper and lower radially extending surfaces adjacent its upperlower ends, said fuse tube being free to move axially relative to saidsleeve member, a rupturable fuse link extending axially through saidfuse tube and being electrically connected to said upper contact and tosaid hinge contact member and normally electrically bridging said upperand lower stationary contacts, a collar member rigidly affixed to saidfuse tube and disposed intermediate said upper and lower radiallyextending surfaces on said sleeve member, first and second spring meanssurrounding said fuse tube and being disposed between said collar andsaid upper and lower radially extending surfaces respectively andsupporting said fuse tube in a normal position relative to said sleevemember against axial displacement in upward and downward directionsunder the thrust forces resulting from expulsion of gas from said fusetube incident to rupture of said fuse link and returning said fuse tubeto said normal position after said thrust forces subside.

3. In an open fuse cutout, an elongated insulating member, a lowerstationary contact and a spring biased upper stationary contact mountedin spaced apart relation on said insulating member, a gas evolvingexpulsion fuse tube, upper contact means afixed to said fuse tube andnormally engaging said spring biased contact, said upper contact meansand said spring biased contact being in continuous engagement throughlimited axial displacement of said fuse tube, a rupturable fuse linkextending axially through said fuse tube and being electricallyconnected to said upper contact means and electrically bridging saidlower and upper stationary contacts, a support member supported on saidlower stationary contact and surrounding at least a portion of said fusetube, said fuse tube being free to move axially relative to said supportmember, and resilient means interconnecting said fuse tube and saidsupport member and supporting said fuse tube in a normal positionrelative to said support member against axial displacement in upward anddownward directions and being adapted to be deformed upon axialdisplacement of said fuse tube resulting from expulsion of gas from saidfuse tube incident to rupture of said fuse link and returning said fusetube to said normal position after expulsion of gas from said fuse tubehas ceased, whereby recoil forces resulting from expulsion of gas fromsaid fuse tube are dissipated in said resilient means.

4. In a dropout fuse cutout, an elongated insulating member, a gasevolving expulsion fuse tube, an upper contact affixed to said fusetube, a lower stationary contact on said insulating member, a springbiased upper stationary contact mounted on said insulating member inspaced apart relation to said lower stationary contact and being adaptedto remain in continuous engagement with said upper contact on said fusetube during limited axial displacement of said fuse tube, a hingecontact member supported on said lower stationary contact, a rupturablefuse link within said fuse tube connected to said upper contact andbridging said upper and lower stationary contacts, an arcuate memberdisposed in surrounding relation to a portion of said fuse tube andpivotally connected to said hinge contact member, collar means rigidlyaffixed to said fuse tube, resilient means surrounding said fuse tubeand engaging said arcuate member and said collar means for supportingsaid fuse tube in a normal position relative to said arcuate member andresiliently opposing upward and downward displacement of said fuse tuberelative to said arcuate member under thrust forces resulting fromexpulsion of gas from said fuse tube and returning said fuse tube tosaid normal position relative to said arcuate member after said thrustforces have subsided, whereby said thrust forces are dissipated bybi-directional axial movement of said fuse tube against said resilientmeans.

5. In an expulsion fuse cutout having an elongated insulator, upper andlower stationary contacts mounted in spaced apart relation on saidinsulator, and a rupturable fuse link electrically bridging said upperand lower stationary contacts, and a gas evolving expulsion fuse tubesurrounding said fuse link; a thrust absorbing device including a memberpivotally supported on said lower stationary contact and at leastpartially surrounding said fuse tube and being movable relative to saidfuse tube in a direction parallel to the axis of said fuse tube, andmeans for resiliently interconnecting said fuse tube and said member andfor supporting said fuse tube in a normal position relative to saidmember against axial displacement under the recoil force caused byexpulsion of gas from said fuse tube and returning said fuse tube tosaid normal position after said recoil force has subsided, wherebydisplacement of said fuse tube underthe recoil force incident to ruptureof said fuse link deforms said supportin means and absorbs said recoilforce.

6. In combination with an open type fuse cutout wherein an expulsionfuse tube surrounding a rupturable fuse element is hingedly supportedadjacent its lower end on the lower stationary contact of the cutout; asleeve member surrounding said fuse tube adjacent the lower end, meansfor supporting said sleeve member on said lower stationary contact,recoil absorbing means disposed between said fuse tube and said sleevemember for resiliently supporting said fuse tube in a normal positionrelative to said sleeve member so that said fuse tube is free to moverelative to said sleeve member and is axially displaceable in upward anddownward directions relative to said sleeve member, means on said fusetube for engaging a first po tion of said recoil absorbing means, andmeans on said sleeve member for engaging a second portion of said recoilabsorbing means spaced from said first portion, said recoil absorbingmeans being stressed in response to displacement of said fuse tubeincident to rupture of said fuse element and expulsion of gas from saidfuse tube and being stressed to a relatively less degree when said fusetube is in said normal position and returning said fuse tube to saidnormal position after said fuse element ruptures and the arc isinterrupted, whereby recoil forces exerted on said fuse tube aredissipated in said recoil absorbing means and are not transmitted tosaid lower stationary contact.

7. In the combination defined by claim 6 wherein said recoil absorbingmeans includes an annular member of elastic shock absorbing materialaflixed to the inner periphery of said sleeve member.

8. In the combination defined by claim 6 wherein one of said means forengaging said recoil absorbing means includes collar means and saidrecoil absorbing means includes first and second compression springssurrounding said fuse tube and abutting against opposite sides of saidcollar means.

Relierences Cited by the Examiner UNITED STATES PATENTS 2,328,745 9/43Sandin 200-114 5 2,519,289 8/50 Roman et a1 200-114 2,544,491 3 /51Davis 200-166 2,689,284 9/54 Hill 200-114 2,877,320 3/59 Hill 200-114BERNARD A. GILHEANY, Primary Examinen 10 RICHARD M. WOOD, Examiner.

5. IN AN EXPULSION FUSE CUTOUT HAVING AN ELONGATED INSULATOR, UPPER ANDLOWER STATIONARY CONTACTS MOUNTED IN SPACED APART RELATION ON SAIDINSULATOR, AND A RUPTURABLE FUSE LINK ELECTRICALLY BRIDGING SAID UPPERAND LOWER STATIONARY CONTACTS, AND A GAS EVOLVING EXPULSION FUSE TUBESURROUNDING SAID FUSE LINK; A THRUST ABSORBING DEVICE INCLUDING A MEMBERPIVOTALLY SUPPORTED ON SAID LOWER STATIONARY CONTACT AND AT LEASTPARTIALLY SURROUNDING SAID FUSE TUBE AND BEING MOVABLE RELATIVE TO SAIDFUSE TUBE IN A DIRECTION PARALLEL TO THE AXIS OF SAID FUSE TUBE, ANDMEANS FOR RESILIENTLY INTERCONNECTING SAID FUSE TUBE AND SAID MEMBER ANDFOR SUPPORTING SAID FUSE TUBE IN A NORMAL POSITION RELATIVE TO SAIDMEMBER AGAINST AXIAL DISPLACEMENT UNDER THE RECOIL FORCE CAUSED BYEXPULSION OF GAS FROM SAID FUSE TUBE AND RETURNING SAID FUSE TUBE TOSAID NORMAL POSITION AFTER SAID RECOIL FORCE HAS SUBSIDED, WHEREBYDISPLACEMENT OF SAID FUSE TUBE UNDER THE RECOIL FORCE INCIDENT TORUPTURE OF SAID FUSE LINK DEFORMS SAID SUPPORTING MEANS AND ABSORBS SAIDRECOIL FORCE.